Body schema
Encyclopedia
Body schema is a concept used in several disciplines, including psychology, neuroscience, philosophy, sports medicine, and robotics. There is no consensus on the definition of body schema across these disciplines. The neurologist Sir Henry Head originally defined it as a postural model of the body that actively organizes and modifies 'the impressions produced by incoming sensory impulses in such a way that the final sensation of [body] position, or of locality, rises into consciousness charged with a relation to something that has happened before'. As a postural model that keeps track of limb position, it plays an important role in control of action. It involves aspects of both central (brain processes) and peripheral (sensory, proprioceptive) systems. Thus, a body schema can be considered the collection of processes that registers the posture of one's body parts in space. The schema is updated during body movement. This is typically a non-conscious process, and is used primarily for spatial organization of action. It is therefore a pragmatic representation of the body’s spatial properties, which includes the length of limb
s and limb segments, their arrangement, the configuration of the segments in space, and the shape of the body surface. Body schema also plays an important role in the integration and use of tools by humans.
, an English neurologist who conducted pioneering work into the somatosensory system and sensory nerves, together with British neurologist Gordon Morgan Holmes
, first described the concept in 1911. The concept was first termed "postural schema" to describe the disordered spatial representation of patients following damage to the parietal lobe
of the brain. Head and Holmes discussed two schemas (or schemata): one body schema for the registration of posture or movement and another body schema for the localization of stimulated locations on the body surface. "Body schema" became the term used for the "organized models of ourselves". The term and definition first suggested by Head and Holmes has endured nearly a century of research with clarifications as more has become known about neuroscience
and the brain.
, adaptable
, supramodal, coherent, interpersonal
and updated with movement
.
and visual
, contributes to the representation of the limbs in space. This integration allows for stimuli
to be localized in external space with respect to the body. An example by Haggard and Wolpert shows the combination of tactile sensation of the hand with information about the joint angles of the arm, which allow for rapid movements of said arm to swat a fly.
changes to the body schema are active and continuous. For example, gradual changes to the body schema must occur over the lifetime of an individual as he or she grows and absolute and relative sizes of body parts change over his or her life span. The development of the body schema has also been shown to occur in young child
ren. One study showed that with these children (9- 14- and 19-month-olds), older children handled spoons to optimally and comfortably grip them to feed themselves, whereas younger children tended to reach with their dominant
hand, regardless of the orientation of the spoon and eventual ease of use. Short term plasticity has been shown with the integration of tools into the body schema. The famous Rubber Hand Illusion, has also shown the rapid reorganization of the body schema on the timescale of seconds, showing the high level of plasticity and speed with which the body schema reorganizes. In the Illusion, participants view a dummy hand being stroked with a paintbrush, while their own hand is stroked identically. Participants may feel that the touches on their hand are coming from the dummy hand, and even that the dummy hand is, in some way, their own hand.
, (the sense of the relative position of neighbouring parts of one's body), and tactile information to maintain a three-dimensional body representation. However, other sensory information, particularly visual, can be in the same representation of the body. This simultaneous participation means there are combined representations within the body schema, which suggests the involvement of a process to translate primary information (e.g. visual, tactile, etc.) into a single sensory modality or an abstract, amodal form.
and somatosensory
receptive field
s of parietal bimodal neurons update with hand movement. This plasticity in the receptive field is also important for the ability to use tools.
and visual feedback. As a result, when constant visual input is lost during an activity, such as walking, it becomes impossible for him to complete the task, which may result in falling, or simply stopping. IW requires constant attention to tasks to be able to complete them accurately, demonstrating how automatic and subconscious
the process of integrating touch and proprioception into the body schema actually is.
typically occurs after left parietal lesions. Patients with this disorder make errors which result from confusion between adjacent body parts. For example, a patient may point to their knee when asked to point to their hip. Because the disorder involves the body schema, localization errors may be made both on the patient’s own body and that of others. The spatial unity of the body within the body schema has been damaged such that it has incorrectly been segmented in relation to its other modular parts.
s are a phenomenon which occurs following amputation
of a limb from an individual. In 90–98% of cases, amputees report feeling all or part of the limb or body part still there, taking up space. The amputee may perceive a limb under full control, or paralyzed
. A common side effect of phantom limbs is phantom limb pain. The neurophysiological mechanisms by which phantom limbs occur is still under debate. A common theory posits that the afferent neurons, since deafferented due to amputation, typically remap to adjacent cortical regions within the brain. This can cause amputees to report feeling their missing limb being touched when a seemingly unrelated part of the body is stimulated (such as if the face is touched, but the amputee also feels their missing arm being stroked in a specific location). Another facet of phantom limbs is that the efferent copy
(motor feedback) responsible for reporting on position to the body schema does not attenuate quickly. Thus the missing body part may be attributed by the amputee to still be in a fixed or movable position.
use. Studies recording neuronal activity in the intraparietal cortex in macaque
s have shown that, with training, the macaque body schema updates to include tools, such as those used for reaching, into the body schema. In humans, body schema plays an important role in both simple and complex tool use, far beyond that of macaques. Extensive training is also not necessary for this integration.
The mechanisms by which tools are integrated into the body schema are not fully understood. However, studies with long-term training have shown interesting phenomena
. When wielding tools in both hands in a crossed posture, behavioral effects reverse in a similar way to when only hands are crossed. Thus, sensory stimuli are delivered the same way be it to the hands directly or indirectly via the tools. These studies suggest the mind incorporates the tools into the same or similar areas as it does the adjacent hands. Recent research into the short term plasticity of the body schema used individuals without any prior training with tools. These results, derived from the relation between afterimage
s and body schema, show that tools are incorporated into the body schema within seconds, regardless of length of training, though the results do not extend to other species besides humans.
were generally lumped together, used interchangeably, or ill-defined. In science and elsewhere, the two terms are still commonly misattributed or confused. Efforts have been made to distinguish the two and define them in clear and differentiable ways. A body image consists of perceptions, attitudes, and beliefs concerning one's body. In contrast, body schema consists of sensory-motor capacities that control movement and posture.
Body image may involve a person’s conscious perception of his or her own physical appearance. It is how individuals see themselves when picturing themselves in their mind, or when perceiving themselves in a mirror. Body image differs from body schema as perception differs from movement. Both may be involved in action, especially when learning new movements.
Limb (anatomy)
A limb is a jointed, or prehensile , appendage of the human or other animal body....
s and limb segments, their arrangement, the configuration of the segments in space, and the shape of the body surface. Body schema also plays an important role in the integration and use of tools by humans.
History
Henry HeadHenry Head
Sir Henry Head, FRS was an English neurologist who conducted pioneering work into the somatosensory system and sensory nerves. Much of this work was conducted on himself, in collaboration with the psychiatrist W. H. R. Rivers, by severing and reconnecting sensory nerves and mapping how sensation...
, an English neurologist who conducted pioneering work into the somatosensory system and sensory nerves, together with British neurologist Gordon Morgan Holmes
Gordon Morgan Holmes
Sir Gordon Morgan Holmes CMG CBE FRS was a British neurologist. He is best known for carrying out pioneering research into the cerebellum and the visual cortex....
, first described the concept in 1911. The concept was first termed "postural schema" to describe the disordered spatial representation of patients following damage to the parietal lobe
Parietal lobe
The parietal lobe is a part of the Brain positioned above the occipital lobe and behind the frontal lobe.The parietal lobe integrates sensory information from different modalities, particularly determining spatial sense and navigation. For example, it comprises somatosensory cortex and the...
of the brain. Head and Holmes discussed two schemas (or schemata): one body schema for the registration of posture or movement and another body schema for the localization of stimulated locations on the body surface. "Body schema" became the term used for the "organized models of ourselves". The term and definition first suggested by Head and Holmes has endured nearly a century of research with clarifications as more has become known about neuroscience
Neuroscience
Neuroscience is the scientific study of the nervous system. Traditionally, neuroscience has been seen as a branch of biology. However, it is currently an interdisciplinary science that collaborates with other fields such as chemistry, computer science, engineering, linguistics, mathematics,...
and the brain.
Properties
Neuroscientists Patrick Haggard and Daniel Wolpert have identified seven fundamental properties of the body schema. It is spatially coded, modularModularity
Modularity is a general systems concept, typically defined as a continuum describing the degree to which a system’s components may be separated and recombined. It refers to both the tightness of coupling between components, and the degree to which the “rules” of the system architecture enable the...
, adaptable
Adaptability
Adaptability is a feature of a system or of a process. This word has been put to use as a specialised term in different disciplines and in business operations. Word definitions of adaptability as a specialised term differ little from dictionary definitions...
, supramodal, coherent, interpersonal
Interpersonal relationship
An interpersonal relationship is an association between two or more people that may range from fleeting to enduring. This association may be based on limerence, love, solidarity, regular business interactions, or some other type of social commitment. Interpersonal relationships are formed in the...
and updated with movement
Motion (physics)
In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...
.
Spatial encoding
The body schema represents both position and configuration of the body as a 3-dimensional object in space. A combination of sensory information, primarily tactileSomatosensory system
The somatosensory system is a diverse sensory system composed of the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception . The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal...
and visual
Visual system
The visual system is the part of the central nervous system which enables organisms to process visual detail, as well as enabling several non-image forming photoresponse functions. It interprets information from visible light to build a representation of the surrounding world...
, contributes to the representation of the limbs in space. This integration allows for stimuli
Stimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....
to be localized in external space with respect to the body. An example by Haggard and Wolpert shows the combination of tactile sensation of the hand with information about the joint angles of the arm, which allow for rapid movements of said arm to swat a fly.
Modular
The body schema is not represented wholly in a single region of the brain. Recent fMRI (functional magnetic resonance imaging) studies confirm earlier results. For example, the schema for feet and hands are coded by different regions of the brain, while the fingers are represented by a separate part entirely.Adaptable
PlasticNeuroplasticity
Neuroplasticity is a non-specific neuroscience term referring to the ability of the brain and nervous system in all species to change structurally and functionally as a result of input from the environment. Plasticity occurs on a variety of levels, ranging from cellular changes involved in...
changes to the body schema are active and continuous. For example, gradual changes to the body schema must occur over the lifetime of an individual as he or she grows and absolute and relative sizes of body parts change over his or her life span. The development of the body schema has also been shown to occur in young child
Child
Biologically, a child is generally a human between the stages of birth and puberty. Some vernacular definitions of a child include the fetus, as being an unborn child. The legal definition of "child" generally refers to a minor, otherwise known as a person younger than the age of majority...
ren. One study showed that with these children (9- 14- and 19-month-olds), older children handled spoons to optimally and comfortably grip them to feed themselves, whereas younger children tended to reach with their dominant
Handedness
Handedness is a human attribute defined by unequal distribution of fine motor skills between the left and right hands. An individual who is more dexterous with the right hand is called right-handed and one who is more skilled with the left is said to be left-handed...
hand, regardless of the orientation of the spoon and eventual ease of use. Short term plasticity has been shown with the integration of tools into the body schema. The famous Rubber Hand Illusion, has also shown the rapid reorganization of the body schema on the timescale of seconds, showing the high level of plasticity and speed with which the body schema reorganizes. In the Illusion, participants view a dummy hand being stroked with a paintbrush, while their own hand is stroked identically. Participants may feel that the touches on their hand are coming from the dummy hand, and even that the dummy hand is, in some way, their own hand.
Supramodal
By its nature, body schema integrates proprioceptiveProprioception
Proprioception , from Latin proprius, meaning "one's own" and perception, is the sense of the relative position of neighbouring parts of the body and strength of effort being employed in movement...
, (the sense of the relative position of neighbouring parts of one's body), and tactile information to maintain a three-dimensional body representation. However, other sensory information, particularly visual, can be in the same representation of the body. This simultaneous participation means there are combined representations within the body schema, which suggests the involvement of a process to translate primary information (e.g. visual, tactile, etc.) into a single sensory modality or an abstract, amodal form.
Coherent
The body schema, to function properly, must be able to maintain coherent organization continuously. To do so, it must be able to resolve any differences between sensory inputs. Resolving these inter-sensory inconsistencies can result in interesting sensations, such as those experienced during the Rubber Hand Illusion.Interpersonal
It is thought that an individual’s body schema is used to represent both one’s own body and the bodies of others. Mirror neurons are thought to play a role in the interpersonal characteristics of body schema. Interpersonal projection of one’s body schema plays an important role in successfully imitating motions such as hand gestures, especially while maintaining the handedness and location of the gesture, but not necessarily copying the exact motion itself.Updated with movement
A working body schema must be able to interactively track the movements and positions of body parts in space. It has been shown that the visualVisual system
The visual system is the part of the central nervous system which enables organisms to process visual detail, as well as enabling several non-image forming photoresponse functions. It interprets information from visible light to build a representation of the surrounding world...
and somatosensory
Somatosensory system
The somatosensory system is a diverse sensory system composed of the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception . The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal...
receptive field
Receptive field
The receptive field of a sensory neuron is a region of space in which the presence of a stimulus will alter the firing of that neuron. Receptive fields have been identified for neurons of the auditory system, the somatosensory system, and the visual system....
s of parietal bimodal neurons update with hand movement. This plasticity in the receptive field is also important for the ability to use tools.
Deafferentation
The most direct of related disorders, deafferentation occurs when sensory input from the body is reduced or absent, without affecting efferent, or motor, neurons. The most famous case of this disorder is "IW", who lost all sensory input from below the neck, resulting in temporary paralysis. He was forced to learn to control his movement all over again using only his conscious body imageBody image
Body image refers to a person's perception of the aesthetics and sexual attractiveness of their own body. The phrase body image was first coined by the Austrian neurologist and psychoanalyst Paul Schilder in his masterpiece The Image and Appearance of the Human Body...
and visual feedback. As a result, when constant visual input is lost during an activity, such as walking, it becomes impossible for him to complete the task, which may result in falling, or simply stopping. IW requires constant attention to tasks to be able to complete them accurately, demonstrating how automatic and subconscious
Subconscious
The term subconscious is used in many different contexts and has no single or precise definition. This greatly limits its significance as a definition-bearing concept, and in consequence the word tends to be avoided in academic and scientific settings....
the process of integrating touch and proprioception into the body schema actually is.
Autotopagnosia
AutotopagnosiaAutotopagnosia
From the Greek a and gnosis, meaning “without knowledge”, and topos, meaning "place", autotopagnosia virtually translates to the “lack of knowledge about one’s own space,” and is clinically described as such.Autotopagnosia is a form of agnosia, characterized by an inability to localize and orient...
typically occurs after left parietal lesions. Patients with this disorder make errors which result from confusion between adjacent body parts. For example, a patient may point to their knee when asked to point to their hip. Because the disorder involves the body schema, localization errors may be made both on the patient’s own body and that of others. The spatial unity of the body within the body schema has been damaged such that it has incorrectly been segmented in relation to its other modular parts.
Phantom limb
Phantom limbPhantom limb
A phantom limb is the sensation that an amputated or missing limb is still attached to the body and is moving appropriately with other body parts. 2 out of 3 combat veterans report this feeling. Approximately 60 to 80% of individuals with an amputation experience phantom sensations in their...
s are a phenomenon which occurs following amputation
Amputation
Amputation is the removal of a body extremity by trauma, prolonged constriction, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on individuals as a preventative surgery for...
of a limb from an individual. In 90–98% of cases, amputees report feeling all or part of the limb or body part still there, taking up space. The amputee may perceive a limb under full control, or paralyzed
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
. A common side effect of phantom limbs is phantom limb pain. The neurophysiological mechanisms by which phantom limbs occur is still under debate. A common theory posits that the afferent neurons, since deafferented due to amputation, typically remap to adjacent cortical regions within the brain. This can cause amputees to report feeling their missing limb being touched when a seemingly unrelated part of the body is stimulated (such as if the face is touched, but the amputee also feels their missing arm being stroked in a specific location). Another facet of phantom limbs is that the efferent copy
Efference copy
right|thumb|282px|Efference copies are created with our own movement but not those of other people. This is why other people can tickle us but we cannot [[tickle]] ourselves .Efference copy is an internal copy created with a motor command of its predicted movement and its...
(motor feedback) responsible for reporting on position to the body schema does not attenuate quickly. Thus the missing body part may be attributed by the amputee to still be in a fixed or movable position.
Tool use
Not only is it necessary for the body schema to be able to integrate and form a three-dimensional representation of the body, but it also plays an important role in toolTool use by animals
Tools are used by some animals, particularly primates, to perform simple tasks such as the acquisition of food, or grooming. Originally thought to be a skill only possessed by humans, tool use requires some level of intelligence. Primates have been observed exploiting sticks and stones to...
use. Studies recording neuronal activity in the intraparietal cortex in macaque
Macaque
The macaques constitute a genus of Old World monkeys of the subfamily Cercopithecinae. - Description :Aside from humans , the macaques are the most widespread primate genus, ranging from Japan to Afghanistan and, in the case of the barbary macaque, to North Africa...
s have shown that, with training, the macaque body schema updates to include tools, such as those used for reaching, into the body schema. In humans, body schema plays an important role in both simple and complex tool use, far beyond that of macaques. Extensive training is also not necessary for this integration.
The mechanisms by which tools are integrated into the body schema are not fully understood. However, studies with long-term training have shown interesting phenomena
Phenomenon
A phenomenon , plural phenomena, is any observable occurrence. Phenomena are often, but not always, understood as 'appearances' or 'experiences'...
. When wielding tools in both hands in a crossed posture, behavioral effects reverse in a similar way to when only hands are crossed. Thus, sensory stimuli are delivered the same way be it to the hands directly or indirectly via the tools. These studies suggest the mind incorporates the tools into the same or similar areas as it does the adjacent hands. Recent research into the short term plasticity of the body schema used individuals without any prior training with tools. These results, derived from the relation between afterimage
Afterimage
An afterimage or ghost image or image burn-in is an optical illusion that refers to an image continuing to appear in one's vision after the exposure to the original image has ceased...
s and body schema, show that tools are incorporated into the body schema within seconds, regardless of length of training, though the results do not extend to other species besides humans.
Confusion with body image
Historically, body schema and body imageBody image (medicine)
Body image is a medical term, often used in the context of describing a patient's cognitive perception of their own body. The medical concept began with the work of the Austrian neuropsychiatrist and psychoanalyst Paul Schilder whose masterpiece The Image and Appearance of the Human Body was first...
were generally lumped together, used interchangeably, or ill-defined. In science and elsewhere, the two terms are still commonly misattributed or confused. Efforts have been made to distinguish the two and define them in clear and differentiable ways. A body image consists of perceptions, attitudes, and beliefs concerning one's body. In contrast, body schema consists of sensory-motor capacities that control movement and posture.
Body image may involve a person’s conscious perception of his or her own physical appearance. It is how individuals see themselves when picturing themselves in their mind, or when perceiving themselves in a mirror. Body image differs from body schema as perception differs from movement. Both may be involved in action, especially when learning new movements.